Air blast circuit breakers



Jan. 24, 1961 H. FORWALD AIR BLAST CIRCUIT BREAKERS Filed May 15, 1958 Iii I l. 0 305/: 6 4m 2 f n 2 2 INVENTOR 170a korz Tom a Z62 BY 2) flffo m e United States Patent AIR BLAST CIRCUIT BREAKERS Haakon Forwald, Ludvika, Sweden, assignor to Allmanna Svenska Elektriska Aktiebolaget, Vasteras, Sweden, a corporation of Sweden Filed May 15, 1958, Ser. No. 735,619

Claims priority, application Sweden May 23, 1957 1 Claim. (Cl. 200-148) The present invention concerns a circuit breaker of the kind having a plurality of containers filled with compressed air arranged on pillar insulators. In said containers breaking gaps are arranged, the stationary contact of which is carried by a leading through insulator projecting into the container. Its movable contact, which is provided with an outlet channel for the extinguishing air, is carried by an operating mechanism attached to the said container. The invention is chiefly characterized in that the movable contact consists of a pipe formed member joined with an operating piston, which member is provided with a valve disc concentric with the outlet channel, and with an axial channel leading from a space on one side of the operating piston and terminating on the surface of the valve disc between the tightening surface and the inner opening of the outlet channel. The valve disc, which is joined with the movable contact, tightens against the valve seat, which is carried by the said leading through insulator and is concentric with the contact members of the stationary contact. The valve seat has a diameter larger than that of the stationary contact, so that the sealing means of the air blast valve will be in front of the contact gap in the direction of the air blast from the container.

When the circuit breaker is closed, the breaking gap will be under atmospheric pressure.

By the invention the operating mechanism for a movable contact With an outlet channel having an area larger than the outlet opening at the breaking gap can be made very simple and the whole operation can be performed by a single operating valve, i.e. an operating valve at the lower end of the carrying insulator. This simplification is reached because the force acting on the movable contact in opening direction, which is generated by the pressure in the container, is entirely or partly compensated by the fact that the container and a space on the one side of the operating piston are in communication with each other, when the breaking gap is open. This equilibrium of the forces will automatically be independent of the pressure variations in the container, which is a very great advantage. Generally the movab'e contact is moved back to the closed position by a spring, although it is possible to dimension the mechanism in such a way that the air pressure acting in closing direction on the operating piston may assist in moving back the contact to its closed position. The said spring is therefore given only such a strength that is able to exert a sufficient contact pressure, if the air pressure in the container should disappear.

In the accompanying drawing a form of the invention is shown. In the figure, 1 designates a compressed air container carried by a pillar insulator, not shown in the figure, by which it will be in permanent communication with a compressed air source. A leading through insulator 2, which is attached to the container 1 by means of the flange 3 and the bolts 4, carries the stationary contact of the breaking gap, which is built up by a number of contact blocks 6 arranged in a disc 5, which are ice actuated in a direction towards the movable contact of the breaking gap by the springs 7. The disc 5 is joined with the leading through bolt 8 and is forced against the sealing ring 9 between the disc 5 and the flat end surface of the insulator 2. The innermost part of the leading through insulator is designed as an arcing contact 10. The disc 5 serves as a valve seat for the air blast valve and is provided with an annularly formed sealing ring 11. The movable contact 12 of the breaking gap is formed as a pipe and provided with a large outlet channel 13 for the air blast. The movable contact carries a valve disc, which in the closed condition of the break ing gap seals tightly against the ring 11. The air blast valve is thus on the up-stream side of the breaking gap. The movable contact is provided at its lower part with a piston 14', which is movably arranged in a housing 15 attached to the lower part of the container 1 by means of bolts 16. 17, 18, 19 and 20 are sealing rings and 21 elements transferring current from the housing 15 to the movable contact 12. 22 is an elastic member limiting the motion of the movable contact. The spring 23 actuates the movable contact 12 and the valve disc 14" in direction towards the contact blocks of the stationary contact and the sealing ring 11. The space 24 above the piston 14' is by the channel 25 in the housing and the channel 26 in the container 1 as well as by conductors, not shown in the figure, in communication with a control valve for the operation of the breaking gap. The space 27 below the piston 14 communicates through the channel 28 in the movable contact 12 with the space 29 between the disc 5 and the upper part of the movable contact 12.

The operating mechanism acts in the folowing way: When the breaking gap is closed, the space 24 is, through channel 26 and said control valve, not shown, in communication with the surrounding atmosphere. The space 27 is by the channel 28, the space 29, the openings be tween the contact blocks 6 and the channel 13 also in communication with the surrounding atmosphere. The movable contact 12 and the valve disc 14" joined with it will then be forced against the disc 6 of the stationary contact and the valve seat 11. The breaking gap will be opened when the space 24 above the piston 14' is supplied with operating air from a compressed air source through said air bfast control valve, not shown on the figure, so that the force acting on the piston 14' will be able to move the contact to its lower position. When the valve disc 14' has left the valve seat 11 compressed air will flow out from the container 1 through the hollow contact 12, so that the breaking arc is attacked. The pressure between the tightening surface of the blast valve and the outlet opening of the contact 12 will then rise to practically the same level as in the container. so that air will flow through the channel 28 in the contact 12 to the space 27 below the piston 14'. Hereby a force acting in closing direction is attained, which can be brought to balance the force, acting on the movable contact, generated by the pressure in the container. so that a comparatively small spring 23 may be able to move the movable contact back to its upper position, when the space 24 is evacuated through the said operating valve.

I claim as my invention:

An air blast circuit breaker having a container permanently fi'led with compressed air, said breaker comprising a leading through insulator projecting into the said container, a stationary contact carried by said insulator, a movable contact enclosed in the container and formed with an outlet channel therein for the escape of extinguishing air from the container, said outlet channel having an inlet opening facing the stationary contact, an operating piston connected to the movable contact, means 3 to supply fluid under pressure to one side of said piston to move the movable contact away from the stationary contact, a blast valve comprising a valve disc with a tightening surface formed around the inlet opening and a valve seatfor said valve disc formed on the stationary contact,

spring means operatively engaging said valve disc to move it toward said valve seat, said valve disc being in fixed relation to the operating piston, said movable contact having an orifice therein between the tightening surface and the inlet opening in permanent communication with said outlet channel and having a channel therein leading from the other side or the operating piston to Said orifice.

References Cited in the file of this patent UNITED STATES PATENTS Strorn Jan. 18, 1949 FOREIGN PATENTS Austria Sept. 10, 1954 France June 18, 1956 

